The invention relates, in general, to heat transfer equipment which can be used in many types of chemical processes and, more particularly, to a shell and tube type of heat transfer device having a bed of free-flowing granular material with tubes imbedded therein, said tubes being coiled in concentric layers on cylindrical surfaces around an axis and being connected at both ends of the device to pipe collectors.
Heat transfer equipment having a bed with tubes imbedded therein are used to perform many chemical and adsorption processes. In this type of equipment, the substance to be treated, which may be a liquid and/or gas, flows through the bed, which may be a free-flowing catalyst or an adsorption material. A heat transfer medium flows through the tubes to either supply or remove heat by indirect heat exchange with the substance(s) flowing through the bed. From time to time, it is necessary to empty the equipment to perform maintenance work and/or to replace the free-flowing granular material. In such cases, a drain line may be attached to the bottom end of the container to remove the free-flowing granular material. Frequently, the granular material is caked together and does not drop out of the equipment. In many instances, the caked material near the bottom of the equipment holds back the granular material above it and prevents the gravity discharge of the bulk of the granular material.
In conventional heat transfer equipment having a shell and coil tube design and a bed of granular material, the tubes at the end of the bed extend to a tube sheet or collector either individually from the point at which they emerge from the coil or else the tubes are formed into bundles which pass into a tube sheet or header. It is usually difficult and often nearly impossible to mechanically empty the bed of granular material in this type of equipment because the top of the tube coils are covered in large part by the tubes running to the collector or tube sheet. Other problems occur in this type of equipment when the substance to be treated is a liquid. For example, if the liquid is introduced at the top of the equipment, the liquid flows through the bed in a relatively uncontrolled manner and is channeled along the tubes leading to the tube sheet. This results in a nonuniform distribution of the liquid in the bed and a lower efficiency of the unit.